1. Field of the Invention
The present invention relates to novel tylosin derivatives which are macrolide antibiotics and more particularly, to novel tylosin derivatives which are chemically produced.
2. Description of the Prior Art
Tylosin is classified into the oldest class of macrolide antibiotics and has been widely used as agents for treating infectious diseases of animals and as feed additives. In recent years, a variety of derivatives have been proposed by chemical or biological conversion, with attempts to enhance its antibacterial activity and at the same time, improve its ability of absorption and excretion in vivo.
As those obtained by the chemical conversion, there are various acyl derivatives of the 4"-hydroxyl group on tylosin, for example, those described in U.S. Pat. No. 4,205,163, etc.; and there are those described in, for example, U.S. Pat. No. 4,092,473, etc. as the derivatives obtained by the biological conversion.
These known tylosin derivatives described above all exhibit improved antibacterial activity against various pathogenic organisms in in vivo test and an enhanced ability of absorption and excretion of the medicament in vivo, as compared to tylosin.
However, these derivatives involved drawbacts as medicaments for treating infectious diseases because derivatives having a high antibacterial activity have poor stability in vivo (for example, they are readily decomposed by liver homogenate of mammals, etc.), or conversely, those having an improved in vivo stability show only poor antibacterial activity against drug-resistant bacteria in specific clinical fields, or the like.